Bushing for spark plugs



W. ,B. SMITS BUSHING FOR SPARK PLUGS Filed Aug. 19, 1949 rill/l IN VEN TOR WYI'ZE 'BEYE SM/TS KW/ M A T TORNE Y Oct. 27, 1953 i W 9 a a Patented Oct. 27,1953

UNITED 2,657,248 BUSHING FOR SPARK PLUGS Wytze Beye Smits, Voorburg,

signor to Smitsvonk N.

lands Netherlands, as- V., Rijewijk, Nether- Application August 19, 1949, Serial No. 111,107

In the Netherlands June 27, 1949 3 Claims. (Cl. 123- 169) The invention relates to low tension spark plugs and more particularly to the construction and. composition. of the bushing therefor.

The bushing for a spark plug according to the invention is to be distinguished from that for use with the usual high tension spark plugs. With these high tension spark plugs the gas tightness is obtained by enclosing the unitary insulating member between elastic rings or by using pure polished conical pan-kings. Either the packing sealing of the bushing to the metallic inner element must be obtained by polishing these elements on each other, after the insulating member is cemented in a special way.

pole and the outer body may The requirements of insulation a low voltage a center pole. According to the invention a material is supplied the plug body and the center pole in the of which very finely divided particles are movably introduced. These particles act to seal treat If a pressure, for example the explosion pressure, is applied to the material, this powder will be pressed in the possible little air channels, still present in the material, which channels are thereupon clogged. The entire material functions as a labyrinth sealing and the gas tightness therefore is assured. The material may be such and. mechanical load.

To satisfy to the requirements of insulation the pressed in material must have a suiiicient electrical resistance and dielectric strength at all mechanical and thermic loads so that lateral discharges and ruptures will not result.

In practice the plugs may be exposed to a very high temperature, especially in air cooled motors. to resist to mensional changes.

To increase the insulation creepage distance to prevent spark over, the end of the pressed in powder body which is exposed to the ignition In the drawing:

Fig. 1 shows partially an elevation and partially a cross section of a plug embodying the invention.

Figs. 2 and 3 are two cross sections of the bottom end of the pressed in powder body.

The plug according to the invention comprises the usual plug body I, which at the bottom end is provided with a thinner projection 3 with a screw thread 2, which can be threaded in the motor block. At the top th plug body I carries the usual porcelain insulating cap 4, which is fixed, for example, on a vertically extending axial member 5 and under the retaining rim la; the axial member 5 carries at its upper end a nut 8 and a clamp l :for the electric conductor. The internal screw thread 8 in axial member 5 serves, forexample, to connect a spark element (not shown).

A free space is provided between the spark body I and the axial member 5, which according to the invention is filled with a pressedin powder material 9, which attaches to the wallsby reason of the fact that these are provided with grooves 18 or other irregularities.

The pulverized material 9 may consist ef-ieldspar of a relatively coarse grain mixed with very finely divided steatite and mica powders, to which a vitreous powder having a low melting point is added. Other well known materials of similar properties may also be used.

The upper side H and the under side l2.of the pulverized material 9 can be hardened by a local heat treatment or by the adding of certain materials, so that the enclosing of the powder mixture is assured with absolute certainty.

From frequent experiments .it is evident that the plugs according tothe invention remain satisiying the most rigorous requirements of gas tightness during the whole lifetime. The spark over resistance may be increased by arranging the underside {2 as illustrated in Figures 2 and 3. According to Fig. 2 the underside isa conical surface l3, while according to Fig. 3 the underside l2 is provided withanexcavation M or the like. With either of these constructions theelectrical creepage distance over the insulation between the axialmember 5 .andthe plug body I is greatly increased so that electrical iailure is prevented.

1 ac rd n pt rh ip filt fi on j 510 age is used, the insulating layer 9 may be thin and it is not necessary to use mica or similar materials for such thin insulating layers. This layer need not to exceed a thickness of about I claim:

1. In a spark plug for low tension ignition, comprising a hollow electrically conductive body member and an electrically conductive axial member dis O Y m mbe posed in the axial memb posed within and spaced from the r, a'gas pressure resistant filling disspace intermediate the body and the er, said filling comprising tightly packed pulverized electrically insulative material of relatively coarse grain mixed with a comparatively finely divided insulative powder, whereby u on pp powder wi ication of gas pressure to the filling, the 11 tend to block the interstices between the relatively coarse grains thereby providing a 'labyrinthsealing effect and a low melting point vitreous material for melting only at the outer surfaces to retain the filling.

2. A spark plug as in claim 1 in which the filling comprises a powder capable of being hardenedby subjection to a treatment which differs from conditions likely to be encountered in operation of the spark plug, said treatment having been ;ap plied to the filling to provide hardened portions therein at surface areas thereof.

3. A spark plug according to claim 2 in which the powder is a vitreous material of low melting point and the treatment includes heating to a temperature above the melting point.

References WYTZE BEYE SMITS.

Cited in the file of this patent UNITED STATES PATENTS Number Number Name Date .Nash l Mar. 19,1891 Garrison et-al Apr. 7,1914 Moore -Mar. 15,1921 Hastings Feb. 9, 1937 Rohde "Nov. 15, 1938 Rabezzana 'Mar. '7, 1939 F REIGN PATENTS Country Date G ea B a Ma A 

